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首页> 外文期刊>International Journal of Biometeorology: Journal of the International Society of Biometeorology >Solar ultraviolet-B and photosyntheticaliy active irradaance in the urban sub-canopy: a survey of influences
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Solar ultraviolet-B and photosyntheticaliy active irradaance in the urban sub-canopy: a survey of influences

机译：城市子冠层中太阳紫外线B和光合作用的主动辐照度：影响调查

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摘要

Stratospheric ozone loss in mid-latitudes is expected to increase the ultraviolet-B (UVB) radiation at the earth's surface. Impacts of this expected increase will depend on many factors, including the distribution of light in other wavelengths. Measurements of the photosyntheticaliy active radiation (PAR) and UVB irradiance were made under clear skies at an open field and under the canopy of scattered trees in a suburban area in W. Lafayette, Indiana, USA (latitude 40.5°). Results showed that when there was significant sky view, the UVB penetration into sub-canopy spaces differs greatly from that of PAR. The UVB T_(canopy) (transmittance; irradiance below canopy/irradiance in open) was inversely related to sky view. The UVB irradiance did not varyas greatly between shaded and sunlit areas as did PAR. Analysis of measurements made near a brick wall indicated that the leaf area of a canopy and the brick wall primarily acted to block fractions of the sky radiance and contributed little scattered UVBto the horizontal plant. A model was developed to predict the UVB and PAR T_(canopy) based on diffuse fraction, sky view, and porosity of the crown(s) through which the beam is penetrating. The model accounted for the UVB and PAR T_(canopy) to within 0.13 and 0.05 root mean squared error (RMSE), respectively. Analysis of the errors due to model assumptions indicated that care must be taken in describing the sky radiance distribution, the porosity of trees, the penetration of diffuse radiation through porous trees, and the location of sky-obstructing trees and buildings.
机译：预计中纬度地区的平流层臭氧损失将增加地球表面的紫外线B（UVB）辐射。这种预期增加的影响将取决于许多因素，包括其他波长的光的分布。在美国印第安纳州拉法叶（W. Lafayette）郊区（纬度40.5°）的郊区，在晴朗的天空下，在开阔的田野和零星树木的树冠下，对光合作用活性辐射（PAR）和UVB辐照度进行了测量。结果表明，当有明显的天空视野时，UVB进入亚冠层空间的穿透性与PAR的差异很大。 UVB T_（冠层）（透射率;低于冠层的辐照度/开放中的辐照度）与天空景观成反比。在阴暗和阳光照射的区域，UVB辐照度没有像PAR那样变化很大。对在砖墙附近进行的测量的分析表明，冠层的叶面积和砖墙主要起阻挡天空辐射的作用，对水平植物的UVB散射很小。开发了一个模型，以基于光束的穿透比例，漫射率，天空视图和冠的孔隙率来预测UVB和PAR T_（冠层）。该模型将UVB和PAR T_（冠层）解释为分别在0.13和0.05均方根误差（RMSE）之内。对由于模型假设而引起的误差的分析表明，在描述天空辐射度分布，树木的孔隙度，扩散辐射通过多孔树木的穿透以及阻碍天空的树木和建筑物的位置时必须格外小心。

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